The electrochemical reaction which occurs in a fuel cell power plant produces water as a by-product. Water is also used as a coolant in the power plant to control cell temperature, since the reaction is an exothermic reaction. Water in the form of steam is also used in the operation of the power plant in the reforming of raw hydrocarbon fuel to hydrogen rich fuel suitable for consumption in the cells. Since water is produced by the plant and is also used to operate the plant, fuel cell power plants will include water circulation systems wherein water will be retrieved, stored, cleaned, and recirculated through the coolant system of the plant. Some water in the form of steam will be comsumed by the power plant in the fuel reforming process, however, it is generally the case that more water will be created in the plant by the electrochemical reaction than will be comsumed by the plant in the form of steam.
In view of the aforesaid, there is a need to periodically drain the water circulation and storage system in the fuel cell power plant. Since the water found in the fuel cell system contains contaminants such as ammonia, carbon dioxide, and system corrosion products, and also contains clean water which has been processed through filters and demineralizing beds, care must be taken to ensure that the water discharged from the plant is clean, and not contaminated. Environmental protection requires that water discharged to the environment have very low levels of contaminants. Thus it is desirable to have a discharge system in the power plant which could discharge only the cleanest water in the system, and one that would operate automatically.